A paper just published on line in Clinical Cancer Research has attempted to project the prostate cancer-specific mortality rates of men managed by active surveillance (followed by radical prostatectomy if and when necessary) as compared the disease-specific mortality rates of men treated with an immediate radical prostatectomy.
Xia et al. created a mathematical “simulation model” that combined (a) data on time from diagnosis to treatment under active surveillance and associated disease progression (from the Johns Hopkins active surveillance cohort of 769 patients); (b) data on time from radical prostatectomy to recurrence from the 3,470 cases in the CaPSURE database with clinical T stage ≤ T2a; and (c) data on time from recurrence to prostate cancer death from men with a T stage ≤ T2a among a Johns Hopkins cohort of 963 patients whose disease recurred after radical prostatectomy.
The authors then used these data to project outcomes for a hypothetical cohort of men aged between 40 and 90 years with low-risk prostate cancer (clinical stage ≤ T2a, Gleason score ≤ 6, and PSA level ≤ 10 ng/ml).
Here are their findings:
- 2.8 percent of men on active surveillance in the hypothetical cohort would die of prostate cancer within 20 years after diagnosis.
- 1.6 percent of men given an immediate radical prostatectomy would die of prostate cancer within 20 years after diagnosis.
- The average projected increase in life expectancy associated with immediate radical prostatectomy (as opposed to initial active surveillance) was 1.8 months.
- Men on active surveillance would — on average — remain free of treatment for an additional 6.4 years relative to men treated immediately.
Xia et al. conclude that,
Active surveillance is likely to produce a very modest decline in prostate cancer-specific survival among men diagnosed with low-risk prostate cancer but could lead to significant benefits in terms of quality of life.
In a media release issued by the American Association for Cancer Research, the publisher of Clinical Cancer Research, Dr. Ruth Etzioni (the senior author of the study) is quoted as follows:
We are now diagnosing many more men with low-risk prostate cancer, a large fraction of whom would never have known they had disease in the absence of screening. These men have cancers that may not have caused them harm if they had not been detected through screening, and we are faced with the dilemma that not all of these men will benefit from treatment.
She goes on to state that:
Although this is not a new result, it is confirmation of what we expected and it substantiates data from previous studies looking at watchful waiting. Very few men with low-risk disease die from prostate cancer regardless, and the difference between treatments appears to be very modest.
Dr. Etzioni also acknowledges that — to date — we know relatively little about the differences between the quality of life between these two groups of patients. We obviously know that immediate treatment is associated with short- and long-term side effects, including impotence and incontinence. However, active surveillance might also have an effect on patients’ quality of life.
That 6-year treatment-free interval means that men who choose active surveillance will not have to endure treatment side effects during that time, but whether that is replaced by a negative impact on quality of life because of anxiety or repeat biopsies is not well known.